Interpretive Summary: Nestmate recognition results in acceptance or rejection of intruders in social insect colonies. The recognition process is composed of the chemical cues, a neural template, and a behavioral response. Acceptance requires that the cues of the intruding worker match the neural template of the resident worker. If the cues do not match, then the resident becomes aggressive toward the intruder. Cuticular hydrocarbons have long been implied as nestmate recognition cues in social insects, but this supposition has been supported only by circumstantial evidence. A scientist at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville, Florida and colleagues from the University of Tel Aviv, Tel Aviv, Israel, have for the first time directly linked hydrocarbons and behaviors associated with nestmate recognition in the ant, Cataglyphis niger. These results advance our understanding of nestmate recognition in social insects. The recognition process is key to the protection of social insects from intrusions from predators, parasites, pathogens, as well as competing insect species. Understanding this process may allow better utilization of parasites and pathogens against pest social insects, such as the fire ant.

Technical Abstract:
Nestmate recognition in social insects involves matching chemical cues on the surface of one individual with the experience derived neural template of nestmate discriminators of another individual. The role of hydrocarbons as nestmate recognition cues in social insects has long been supported only by circumstantial evidence. We report here the first direct experimental evidence that hydrocarbons rather than neutral or polar lipids, are responsible for nestmate recognition in the ant Cataglyphis niger. Isolated hydrocarbons, but not other lipids, applied to one of a pair of live nestmates or alien ants, significantly modified the aggressive behavior in the direction expected if hydrocarbons were nestmate recognition discriminators. Treated ants behavior did not change supporting the view that the existing template was not altered by the treatment. Elevation of aggressive behavior by artificially exposing the ant to an alien odor was more pronounced than its reduction when exposed to nestmate odor. We conclude that during the recognition process the ants rely more on differences between the template and label, rather than on the similarities between the two.